Improvement in cut-off valves



4UNITED STATES PATENT OFFICE."

CHARLES H. PARSHALL, OF DETROIT, MICHIGAN.

IMPROVEMENT IN CUT-OFF VALVES.

Specification forming part of Letters Patent No. 43,334, dated June 28,1864.

To all whom, it may concern.'

Be it known that I, CHARLES H. PAR- SHALL, of the city of Detroit, inthe county of Vayne, in the State of Michigan, have invented a new andimproved mode of balancing slide cutAoft's used in steam-chests forcutting off steam from the cylinders of steamengines at any point of thepistonstroke; and I do declare that the following is a full and exactdescription thereof, reference being had to .the accompanying drawings,and to the letters of reference marked thereon, forming a part of thisspecification, in which- Figure 1. is a vertical section, A A', ofsteam-chest and cylinder, showing my invention. Figi`2 is a verticalcross section, B B', of steam-chest and cylinder also showing myinvention. Fig. 3 is a perspective view of valve O and plate ,V asfastened to it. Fig. 4is a perspective view of my cut-off G and plate Eas fastened to it.

Similar letters of reference in the four ligures indicate correspondingparts'.

The nature of my invention consists in providing a slide cutoff used insteam-chests for cutting 0E steam from the cylinders of steamengines atany point of the piston-stroke, which cut-oft' will be balanced as tothe pressure on it of the steam in steam-chest, a-nd also as to itspressure on the valve from its own weight, whereby I do away with alarge amount of friction, also require much less steam-power to performa given amount of work, and also diminish the natural wear of themachinery.

To enable others skilled in the art to make and use my invention, I willproceed to describe its construction and operation.

I construct my valve O and valve-seat P in a well-known mode and form,the valve being a rectangular plate, making a steam-tight joint with thevalve-seat, and having in it the usual exhaust concave and ports F F',one for each end of the cylinder It, and to let the steam into itthrough the corresponding ports U U' of the valve-seat P. My valve-seathas also the usual exhaustport S, for conveying 0E the steam after itsuse in the cylinder. I also give motion to the valve O in the wellknownmode by means of a valve-rod, N, to which it is fastened.

I construct my cut-off G in the usual mode and form, being a rectangularplate of suitable thickness, strength, width, and length for itspurpose, and having in it the steam-ports L L', to connect as requiredwith the corresponding ports, F F', of the valve and U U' of thevalveseat. In the usual mode I place it on the valve and give it itssliding motion by means of a cut-oit' rod, J, to which it is fastened,

By means of connecting-standards Y Y' and screws, or by means of solidcasting, or any other convenient means, I fasten a plate, E, of suitablestrength and thickness, firmly to and over the cut-oft' G, parallel toit, and at a suitable distance from it, to allow the steam to passfreely between the plate E and cutoff from one end of the steam-chest tothe other.

The cutoff G and plate E, when thus either made in one piece orotherwise fastened to@LL gether, will move in connection with each otheras one body, G E; also, I construct the plate E so as to be of the samewidtlrv and llength as the cut-off G, so asto have in it openingsopposite corresponding in position and equal in areas to the ports F F'of the cut-off G, and so as to have an upper surface area equal to thelower surface area of the cutoff G.

By means of connectingstandards K and screws, or by means of solidcasting or any other convenient means, I fasten firmly to and over thevalve, and parallel to it, the pla-te V, of suitable thickness andstrength and of theV same upper surface area as the plane lower surfacearea of the valve. When thus fastened, the plate V and valve O will movein connection with each other as one body, O V also, Ifasten the plateV, as above described, at a suitable distance from the valve O, toreceive and allow the sliding between them of my cut-oft' G inconnection with the plate E fastened to it, as hereingdescribed, also,by scraping or other convenient means I cause the lower surface of plateV and upper surface of plate E to make with each other a steam-tightjoint.

Over the center of the exhaust-port S in the valve-seat, and through thecenter of the valve O, I make 'an aperture, D, in order to allow theatmospheric pressure to act through the exhaustport and through suchaperture upon and against the cut-0E G, said aperture D to be of thedimensions hereinafter specified.

My invention, being thus constructed, will operate as follows-that is tosay: The pressure of steam in the steam-chest being removed fromthelower surface of the cut-off G by means of its steam-tight joint withthe valve O, it is also removed from the upper surface of the plate E bymeans of plate V, which makes a steam-tight joint with it, and it is forthis purpose that I use plate V, constructed, fastened, and arranged asherein described. By means of plate E the downward steam-pressure on theupper surface of the cutoft' G is balanced by an equal upward andopposite steam-pressure on the lower surface of plate E; and it is forthis purpose that I use plate E, constructed, fastened, and arranged asherein described. Thus my cut-off G is balanced so that the pressure ofsteam in steamchest neither forces it against the Valve O nor pressesthe plate E against the pla-te V. By means of the aperture D through thecenter of the valve and over the exhaust-port S,I subject the cut olf Gto an atmospheric pressure sufficient, according t0 the usual estimatedweight of the atmosphere, to balance the pressureof the cut-off G on thevalve O from its own weight and that of the parts fastened to it, asherein described. In cases where the cut-off works to a perpendicularvalve, such aperture is not made or required, and in cases where itworks on an inclined valve such aperture will vary in size under varyingangles cf inclination, and consequent Varying pressures of the eut-oft'G in the valve O from its own weight and that of the parts fastened toit, as herein described.

By thus b( lancing my cut-off I do away with a large amount of frictionon the cuto valve and other parts of the engine; also with the increaseof steam used to overcome thefriction thus done away with, and also withthe wear of machinery naturally caused by the friction thus done awaywithV and by the increase of steam to overcome it.

Letters of reference are marked on the accompanyin g drawings, notbefore referred to, as follows, viz., H being cover of the steamchest, Ibeing sides of steam-chest, T being the gland of stuffing-box ofValve-rod N, X being gland of stuffing-box ot' cut-off rod J.

WhatI claim as my invention, and desire to secure by Letters Patent, is-

1. The plate V, constructed, arranged, and used for the purposes andsubstantially as herein shown and described.

2. rIhe balanced cut-off valve G E, constructed and operatingsubstantially as described.

3. The aperture D, in center of valve and l over exhaust-port S,constructed, arranged,

Dated at Detroit, this 28th day of Decem-A ber, A. D. 1863.

CHARLES H. PARSHALL. Witnesses:

CHARLES D. SMITH, J AMEs H. GRIDLEY.

